MT and reflection seismics in northwestern Skellefte Ore District, Sweden

Abstract

A seismic reflection and MT survey was carried out along a 27-km long transect in northwestern Skellefte District, as part of a bigger 3D modeling project. The main motivation for the data acquisition is to elucidate the geologic relationship between the known mineralizations in the Adak mining camp to the north and in the well studied Kristineberg area south of the transect. The seismic reflection data were acquired with a VIBSIST system, and show reflectivity down to 3 s. Apart from the conventional processing for crystalline environments, the seismic data was also subject to an azimuthal binning procedure and crossdip analysis, allowing the orientation of planar reflectors in 3D. Regarding the MT data, it is primarily of good quality along the 17 installed sites. The inversion of the determinant of the impedance tensor yielded a stable 2D resistivity model, dominated by resistors corresponding to the postorogenic intrusions along the transect. Adding the location of the analyzed seismic reflectors in the MT inversion rendered an integrated model that facilitated a preliminary joint interpretation of the data sets. Overall, the results are in good agreement with surface observations and reveal a crude configuration of the geologic units below the transect. The most prominent outcomes are the lateral and depth extent of the large postorogenic intrusions in the area reaching to 5-or 6-km depth, the dimensions of the nearly vertical Brännäs gabbro extending to 6-km depth, and the presence of enhanced conductivities along the transect at about 10 km depth. The latter is probably related to the deep conductor previously identified in the district.

2D and 3D MT in the central Skellefte Ore District, northern Sweden

“…All showed values are percentages. Figure 1: Geological map of the Skellefte District with the location of the MT sites (Hübert et al, 2009(Hübert et al, , 2013García Juanatey et al, 2013a,b) and seismic reflection profiles (Tryggvason et al, 2006;Dehghannejad et al, 2010Dehghannejad et al, , 2012aGarcía Juanatey et al, 2013b), different colours indicate different field campaigns. Major shear zones are the north -south trending Däppis-Näsliden shear zone (DNSZ) and Vidsel-Röjnoret shear system (VRSS).…”

Deep Structure of Nanling-Xuancheng Ore District, Eastern China: Insights from Integrated Geophysical Exploration

“…There are currently various methods and strategies for joint inversion, depending on geological conditions and exploration targets [52][53][54][55]. Among these, the iterative collaborative joint inversion strategy is widely used because it can work without changing existing mature software [56][57][58][59]. Additionally, the real-time human-computer interactive inversion process can make better use of geological experts' understanding, while quickly updating prior information.…”

Joint interpretation of magnetotelluric, seismic and well-log data in Hontomín (Spain)

“…These areas are usually heterogeneously distributed and commonly feature low propagation velocities. This causes unwanted delays in the traces and subsequent disturbances in the coherency of deeper reflections (Juhlin, 1995). Refraction static corrections are standardly used to mitigate this problem (e.g.…”

“…Joint interpretation of seismic and electromagnetic data have proven successful in subsurface characterization (e.g. Harris and MacGregor, 2006;Juanatey et al, 2013;Solon et al, 2015). Hence, a compelling reservoir characterization will benefit from the integration of the structural interpretation, provided by the seismic image, with the electrical properties derived from the MT method (e.g.…”